Help!
I'm making a striped, raglan-sleeved baby sweater (Rowan's "Just Baby" book, "Norton" in case anyone has it). I have the back finished up through the raglan armholes and now I'm on the front. Have the front done up to where I start shaping the armholes (18 stripes plus ribbing). NOW I'm stumped. Here is what it says to do next:

(Section 2) Working all raglan armhole decreases as set by back, dec 1 st at each end of next and 3 foll 4th rows, then on foll 3 alt rows (33 sts)

Okay, I started Section 1--have done this twice and taken it out twice when I realized what happens. Argh.

I'm working in plum and purple. So, my next stripe is to be purple. I cast off 3, placed a marker, then 4 more st. and knit the rest of the row. For the next row, I purl in plum color, casting off 7 at the beginning of the row.

Here is my problem. When it's time to work on Section 2, I need to use the purple yarn, but it's 7 cast-off stitches to the right and not where it should be to knit with it. Am I totally off here? Am I doing this wrong? Not sure if I'm explaining this well enough. Because that side is finished off there is no purple yarn at the beginning stitch, rather it's at the beginning of the cast off stitches.

Any ideas? Am I reading/interpreting this wrong? Also, not sure why they said to place a marker, as there's no mention of it ever again. ??

This sometimes happens when you do colorwork. Yes, as GG suggests, you can cut the yarn and start the row with the purple color. However, if you decide to take out the row, the way to do this is to use the plum to cast off and at the same time carry the purple yarn across the cast off sts (fair isle technique) and drop it at the body. That way it will be in place when you want to pick it up again for the next stripe.
I'm not sure about the marker either. Have you read the finishing directions? It may have to do with aligning the sleeves.